Production rates of existing distillation columns can be limited by reboiler duty, also referred to as reboiler heat duty, or the rate at which heat is transferred from the reboiler to the column. There are a number of reasons that reboiler duty can be insufficient. For instance, the performance of a thermosiphon reboiler can be limited because of fouling, reboiler size, reboiler instability caused by unstable/oscillatory or insufficient fluid flow, or insufficient driving pressure across the reboiler and reboiler channel head. One option for increasing reboiler heat duty for would be to supply supplemental heated fluid to the column using an auxiliary heat exchanger, in addition to the heated fluid from the reboiler. However, this approach generally requires adding one or more large nozzles to the distillation column to supply the additional heated fluid. Unfortunately, this solution is not always practical for large existing columns due to layout or space limitations, or vessel code requirements which require difficult to implement heat treating of the column shell in the area where the new nozzle would be added. Small nozzles are generally unsuitable as the resulting fluid velocities and kinetic energy are generally too high, resulting in excessive nozzle and shell erosion, as well as localized disturbances to the internally flowing fluid velocity and distribution profiles inside the column shell.
It would be desirable to provide a more practical means for increasing the reboiler duty of a thermosiphon reboiler.